The minimum distance of reflector surface from the source for listening the echo of sound is :

(1) 28 m

(2) 18 m

(3) 19 m

(4) 16.5 m

If the amplitude of the sound is doubled and the frequency reduced to one-fourth, the intensity of sound at the same point will be :

(1) Increased by a factor of 2

(2) Decreased by a factor of 2

(3) Decreased by a factor of 4

(4) Unchanged

Intensity level of a sound of intensity I is 30 dB. The ratio $\frac{I}{I_0}$ is (Where I₀ is the threshold of hearing) 

(1) 3000

(2) 1000

(3) 300

(4) 30

Of the following the one which emits the sound of a higher pitch is :

(1) Mosquito

(2) Lion

(3) Man

(4) Woman

Two waves having sinusoidal waveforms have different wavelengths and different amplitudes. They will be having :

(1) Same pitch and different intensity

(2) Same quality and different intensity

(3) Different quality and different intensity

(4) Same quality and different pitch